ATL的offsetofclass中,为啥_ATL_PACKING是8的解释

__ay — Thu, 12 Jan 2012 05:52:00 GMT

解答出处

http://stackoverflow.com/questions/5014061/whats-the-use-of-atl-packing-constant-when-computing-distance-from-the-start-o

C++标准规定:

编译器的类的类型转换对空指针(NULL)特殊处理,即你NULL进行强制类型转化的结果还是NULL,所以….

				static_cast类型转化的时候,_ATL_PACKING的值得是非零就好

C++ Standard 4.10/3 Pointer conversions [conv.ptr]:

An rvalue of type “pointer to cv D,” where D is a class type, can be converted to an rvalue of type “pointer to cv B,” where B is a base class (clause 10) of D. If B is an inaccessible (clause 11) or ambiguous (10.2) base class of D, a program that necessitates this conversion is ill-formed. The result of the conversion is a pointer to the base class sub-object of the derived class object. The null pointer value is converted to the null pointer value of the destination type.

__ay 2012-01-12 13:52 发表评论

学校的数据结构试验题目二--哈夫曼树编码

__ay — Tue, 09 Dec 2008 06:42:00 GMT

摘要: 终于写完了~~我觉得那个解码编码部分还能优化~~ 如果有更好的方法欢迎赐教~~呵呵题目:解法:Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> 1 #include 2 #include 阅读全文

__ay 2008-12-09 14:42 发表评论

学校的数据结构试验题目一背包问题

__ay — Tue, 09 Dec 2008 06:36:00 GMT

题目如下,解法可能不是最好的若有更好解法请赐教
初学算法~望多多指教啊~~

解法:

1
  2
  3 #include <iostream>
  4 #include <windows.h>
  5
  6 #define MAXINPUT 15
  7
  8 using namespace std ;
  9
10 struct stack {
11     int *data ;
12     stack *next ;
13 } ;
14
15
16
17 stack *push(stack *top , int *data )   //压栈
18 {
19     stack *tem =  new stack ;
20
21     tem->data = data ;
22
23     tem->next = top ;
24
25     return tem ;
26 }
27
28 stack *pop(stack *top , int **data)   //出栈
29 {
30     if( top == NULL)
31         return top ;
32     stack *tem ;
33
34     tem = top ;
35
36     *(data) = tem->data ;
37
38     top = top->next ;
39
40     delete tem ;
41
42     return top ;
43 }
44
45 void stackprint(stack *top)  //打印栈内容
46 {
47     while(1)
48     {
49
50     if( top == NULL )
51         break ;
52
53     cout<<*(top->data)<<" " ;
54
55     top = top->next ;
56
57     }
58
59     cout<<endl ;
60 }
61
62
63
64 int sum = 0 , input[MAXINPUT] = {0}  ;
65
66 int main(void)
67 {
68     int count = 0 , T = 0 ;
69
70     cout<<"请输入T值"<<endl ;
71     cin>>T ;
72
73     cout<<"请输入w数组数目"<<endl ;
74     cin>>count ;
75
76     if( count > MAXINPUT )
77     {
78         cout<<"输入溢出"<<endl ;
79         return 1 ;
80     }
81
82     for( int i = 0 ; i < count ; i++ )
83     {
84         cout<<"请输入w["<<i<<"]值"<<endl ;
85         cin>>input[i] ;
86     }
87
88     cout<<endl<<"Loading"<<endl ;
89
90
91
92     stack *top = NULL ;  //初始化栈
93
94     int i = 0  , *temdata = input , *popdata = input , *enddata = &input[count]  ;
95
96     /*
97     栈的非递归调用,
98     先压栈数据,然后依次遍历剩余的数据,满足条件打印,小于预期值就压栈
99     接着遍历剩余数据,遍历这个层次的数据完了就出栈,然后指针+1(指向下一个数据),继续遍历剩余数据
100     */
101
102     while(1)
103     {
104         sum += *temdata ;
105
106         top = push(top , temdata) ;
107
108         if( sum == T )
109         {
110             stackprint(top) ;
111             top = pop(top,&popdata) ;
112             sum -= *popdata ;
113             top = pop(top , &popdata ) ;
114             sum -= *popdata ;
115             temdata = ++popdata ;
116
117         }
118         else if (sum > T )
119         {
120             top = pop(top,&popdata) ;
121             sum -= *popdata ;
122             temdata = ++popdata ;
123         }
124         else if( sum<T )
125         {
126             temdata = ++popdata ;
127         }
128
129         if( (temdata-1) == enddata )
130         {
131             top = pop(top,&popdata) ;
132             sum -= *popdata ;
133             top = pop(top,&popdata) ;
134             sum -= *popdata ;
135
136             temdata = ++popdata ;
137         }
138
139         if( top == NULL &&  popdata == enddata)
140                 break ;
141
142     }
143
144
145
146
147     system("pause") ;
148
149     return 1;
150
151 }
152
153
154

__ay 2008-12-09 14:36 发表评论

C++博客-Ay's Blog@CNSSUESTC-随笔分类-算法 && C/C++

ATL的offsetofclass中,为啥_ATL_PACKING是8的解释

学校的数据结构试验题目二--哈夫曼树编码

学校的数据结构试验题目一 背包问题

学校的数据结构试验题目一背包问题